Electron beam tubes



Sept. 21, 1954 D. s. BOND ELECTRON BEAM TUBES Filed Feb. 25. 1950 n m mn A Patented Sept. 21, 1954 '-ELECT'RQN BEAM TUBES JDonaflxlfS. ""Bond;V"Princeton, N. J., assignor to "RadioGorporation of America, acorporation of .Application-February 25, 1950, Serial No.14;6,282

` fClaims.

VIn electron-lbeam tubes Ofithe kind lin which I am especiallyinterested, l the target vcomprises a multiplicity of subselerrrentalphosphor areas or lines. When thetubeisofthe c'olor-kinescope variety,each phosphorline emits .lightofa Dar- `ticular color component..In'colorikinescopes' as in other line-target tubes, the 'bigproblemisto vkeep l the `beam in register with the phosphor lines.

One 'solution of'4 the problem of'.be'am=toline 4 registry incolor-kines'copes is set forth byZWory- Vkin in his U.' S.Patent:2,41'5,'059," issued. January 28, 1947. "'Zworykinteaches"the'useof control signals generated ."b'y `'a number 'of photo'cells. Eachphotocellis sensitive to'on'e ofthecolors emitted bythe; phosphorflines.vThe"c`ontrolsig nais are employedtoacc'elerate or' deceleratethedeflection of thebeam'fin"accordance 'with its I obviate"'tlre'above-described *and* other -less o apparent objections to `present"dayb'eam-tof-line registry' systems` byproviding -a'catl'iederayr tubecontainingran electronesensitiv-e screen or-'target having' 'discrete'lightremisste Yand signal-generatingr areas. I'dispcselthesignaligenerating"area "adjacent to amarginaledgeofthelight-'emissive area. -'IIence' theY beam in traversing thesignal-'generating indicia may Ibe endowed (by the grid 'of' they gunAof the'4 tube) f-With yany'constant intensity "required togeneratefvernier control signals of a uniformly*"usablel amplitude.

In traversingVv the light-'emissive area, the beam may be varied inintensity,` as `dictated-by Video signals 'appliedf'to the" grid.Without affecting' the amplitudeof'V tne"`controlffsignals picked7 up lfrom thesignal-generating area.

I achieve greater Vaccuracy of bea'incontrol 'when I provide separatebeam-deiecting -elements. for the""scanning and" Vernier Hdeeoting-forces. Thus, "although I may apply `the horizontal `and" verticalscanning forces 4to the beam inthe usual "Way (e: g., through amagneticyoke disposed on the exterior of the tube) -Iv 'prefer to` apply' theVernier deflecting Yforces toone' of a pairof auxiliary electrodes.

2 Allof theseieatures of myV invention vare Villus- Vtrated in theaccompanying `drawing, wherein:

Fig. l is a partly sohematicVbroken-away View in perspective of anelectron-'imagetubecontaining a target er screen electrodehavingrvdiscrete signal-.generating and light-emssive areas. The tube isprovided with a pair of defiecting electrfodes` to which Vernierdeflecting forces, `derived from `the signal-generating target area,'are applied t0 the beam;

FgjZ is an enlarged View in perspective'ofa portion of' thecolor screen.A part of themetallized surface of the screen is rolled'back Vrto revealits phosphor lines;

Fig. 3 is a chart of'a portion ofthe surface of the screen showingvarious .possible positionsv of the beam; and

Fig. l is a curve to which I refer in explaining the operation of mytubeunder the conditions ,indicated in Fig. 3.

In applying my inventionv to `acolor-kinescope, Imay use aconventionalimage-tube'envelope'i having a bulbous portion i and arearwardly extending neckportion 3. The vacuous space between the 'bulband Ineck is continuous. I prefer toY employ the rear surface il of aseparate glass plate '5 as `the foundation of my biepart screen.I-Iov/ever, I may use the Vinner surface or" the window 6 as thefoundation. Alternatively, .fthewindow andneck ofthe envelope-aresuitablyoriented, I may employ a non-transparent foundation plate (notshown). Inany event, the screen ccmprisesa light-emissivearea'l and adiscrete signabgenerating area il. The 'signalgenerating area-ii isdisposed along a marginal edge of the light-emissive-area l. Both ofthese screen areas 'E ands-are accessible to theelectron-beamV t whenthe beam is Vsubjected to -a conventional scanning movement. Thescanningmovement results from-horizontal and 'vertical deflecting forcessupplied by electromagnetic coils .le and il. These coils are disposedat right angles to each other on the neck i of the tube.

An opaque coating l2 on the back of the signalgenerating area 8. of theplate 'conceals that area from theview of an observer looking into theWindow.

The source of the beam il is a conventional electron-gun. The gun whichis shown here comprises an'indirectly heated cathode I3, agrid-ifl and arst anode l5. The grid vcontrols thelintensity of the beamduringfits'excursion across both areas `'i andS ofthescreen. :Apcrtionof the-inner surface of the neck and-*bulb f'ZLhas 1 accnductivelcoatingi it. vflhiscoating;is the.l sec ond anode of thedevice. The outer surface of the light-emissive area 'l may comprise atransparent aluminum nlm il (Fig. 2). This conductive iilrn il may beconnected, as by a lead l, to the second anode i5.

A strip-like conductor I9 is supported, as on insulating beads 29, alongthe outer edge of the signal-generating area 8. A pair of deectingplates 2l, 22 is disposed, in front of the electrongun, in horizontalplanes on opposite sides of the path of the beam 9. The metal strip lecollects the electrified particles or signals emitted by thesignal-generating area 8 when it is hombarded by the beam 9. The signalsimpinging upon the collector electrode are applied through anappropriate servo circuit 23 to the deflecting plate 2|. The other plateis maintained at a high positive potential, for example by connecting itto the second anode I6. When thus applied, the signals operate to impartVernier vertical deilecting forces to the beam. Alternatively, assuggested by Zworykin Patent 2,415,959 (previously mentioned) andZworykin 2,304,755,

' the Vernier or correcting signals may be applied to an appropriate oneof the magnetic deflection coils l or il. In this later connection,however, I call attention to the fact that the coils Il) and Il arecurrent (as distinguished from voltage) actuated devices of highinductance and that the correcting force of the Vernier signals isusually a voltage containing relatively high frequency components.Therefore, the servo circuit 23 may be simplied by applying this voltagedirectly to one of the electrostatic plates 2|, 22, instead ofconverting it into current of the amplitude required to produce anappropriate magnetic deflecting force. One such servo circuit is claimedin co-pending application Ser. No. 146,230, in the name of Donald G.Moore. Another is claimed in application Ser. No. 146,283, now U. S.Patent 2,634,325, in my name jointly with Donald G. Moore. Said patentapplications are led concurrently with the subject case.

In making the screen, I provide its foundation surface 4 with a number(say, two hundred and forty) of groups of (say, three) narrowphosphorstripes or lines, R, B and G. Each line is capable of emittinglight of a particular color component when bombarded by electrons.

As taught by Leverenz in U. S. Patent 2,310,863, when the phosphor lineswhich make up the clifferent groups are to emit blue, green and redlight, respectively, the materials of which the lines are composed maycomprise: Silver-activated zinc sulfide and zirconium silicate for theblue lines B. Alpha-willemite activated with manganese or zinc cadmiumsulfide activated with silver for the green lines G. Chromium-activatedaluminum berylliate or zinc cadmium sulfide activated by silver for thered lines R.

The parallel phosphor-lines R, B and G preferably, though notnecessarily, extend horizontally. In the space between the ends of thelines R, B and G and the edge of the foundation surface li, I provide anumber (in this case, two) or parallel columns C, C of signal-generatingindicia. In the instant case, the indicia take the form ofline-segments, Rl, R2 etc., B1, B2, etc. They are arranged in registerwith the blue (B) and the red (R) lines of each of the several groups ofphosphor lines.

The particular (line-segment) contour and (two-element) code arrangementof the signal-generating indicia here shown is especially llsuited foruse in connection with conventional phosphor-line screens. This is sobecause the simplicity and economy of the code indicia facilitate boththe manufacture of the screen and the design of the control circuitswhich may be associated therewith.

I may employ any of a variety of ray-emissive materials in thesignal-generating area 8. I prefer, however, to use secondary-electronemissive materials in preference to light-emissive or ultraviolet-ray orX-ray or infra-red ray emitters. The use of secondary-electron emissivematerials simplifies the problem of collecting the signalbearingemanations from the code indicia. Thus, as previously pointed out, I mayemploy as the signal-collector electrode a single strip of metal I9. Imay dispose an additional collector electrode (not shown) between thesecond column C' of indicia and the adjacent terminals of thelight-emissive strips, though this is usually unnecessary. The collectorelectrode or electrodes should not prevent the beam from impinging uponany portion of the signal-generating or light- 4emissive areas. Thiscondition is avoided, in the instant case, by mounting the collector i9along the edge of the glass plate 5 in a plane normal to its foundationsurface 4.

One might assume that I should form the indicia Rl, Bl etc. of amaterial having the highest obtainable secondary-electron toprimaryelectron emissive ratio. Such, however, is not necessarily thecase. The principal requirement is that there be a usefully greatdifference in the emissive-ratios of the code marks and the surface 24immediately surrounding the same. Thus, I may make the code marks Bl, Rletc. of a material (e. g. glass or carbon-black) having asecondary-to-primary electron emissive-ratio of less than unity,providing I make the surrounding surface 2li of a material (e. g. silveror aluminum) having an emissive ratio greater than that of the other. Inthe interests of simplicity, however, I prefer to make the code marksor" the more highly emissive material and to use the surface of theglass foundation plate 5 as the contrastingly less-emissive area 2d.

I i'lnd it convenient to refer to the chart of Fig. 3 and to the curveof Fig. d in explaining the manner in which the secondary-electronemissive indicia Bl, Rl, etc. operate to generate signals capable ofeiecting the up or down Vernier adjustment required to bring the beam 9into register with a particular phosphor line.

Let use assume that the beam starts its movement across thesignal-generating area at the various points indicated by the beam spots9, Sa, 9h, 9c or 9d. Let us also assume that the phosphor line uponwhich the beam should impinge is the green line G. In the particulararrangement or code of the signal-generating indicia here shown, thereis a code-mark opposite each of the blue and red phosphor lines (B andR) but none opposite the green line (G). l-Ience, if the beam 9 ismoving along an axis afwhich coincides with the longitudinal axis of thephosphor line G, it will pass through the signalgenerating area 8without encountering either the indicia B1 or R1. Thus, no controlsignal will be generated. Nor is any required, since the beam is whereit should be, i. e., in register with the line G. This condition of nosignal is indicated by the point 9 on the curve of the chart.

If the beam should start its excursion across the signal-generating areaat one of the points indicated by the beam spots da or 9b, i. e., abovethe central axis :v -r, it will encounter the indicia or code mark Bl.Hence, secondary-electrons will be released in a quantity proportionalto the percentage of the total beam area impinging upon the code markB1. As a result, a Vernier beam-delecting signal of the magnituderequired to move the beam the proper distance into register with theline G Will be generated. This condition is indicated by the points 9aand 9b on the curve of the chart. The information necessary to ensurethe proper direction of this movement is supplied to thetime-discriminating means of the servocircuit 23 (Fig. 1) by reason ofthe fact that in the columnar arrangement of the indicia, the rst column(C) is allotted to the down movement.

If, as indicated by the beam spots 9c and 9d, the beam strikes thesignal-generating area at a point beneath the line :v -m, it willencounter a secondary-electron emission code-mark when it reaches thefirst column, C, where it will strike the mark R2. Here again abeam-deliecting signal of the magnitude (indicated by points 9c, 9d onthe left or red curve of the chart) and (upward) direction required tomove the beam the proper distance into register with the greenphosphor-line G.

I have described the screen of the tube of my invention as containing asignal-generating code of a simple yet practical pattern. My disclosurein this respect is intended as illustrative. I may use othersignal-generating line or dot codes for the same purpose (i. e.,beam-toline register), or indeed for other purposes, for example,controlling the focus or the timing of the beam, or for securing linear,vertical, radial or other directional scanning of a high order ofprecision.

I claim as my invention:

1. The combination with an electron-beam tube of the type provided withhorizontal and vertical beam-deecting means and containing a targethaving discrete light-emissive and signal-generating areas upon whichthe beam may successively and repeatedly be directed by said horizontaland vertical beam-deliecting means, of auxiliary beam-deflecting, meansdisposed adjacent to the path of said beam for applying to said beamVernier deecting forces derived from said signal-generating area of saidtarget.

2. The invention as set forth in claim 1 and wherein said auxiliarybeam-deecting means comprises a pair of electrodes disposed insubstantially horizontal planes on opposite sides of the path of saidbeam Within said tube, whereby said Vernier defiecting forces serve todeflect said beam in a vertical direction only.

3. The invention as set forth in claim 2 and wherein saidfirst-mentioned beam-deecting means are of the magnetic type and aredisposed on the exterior of said tube intermediate said target and saidpair of horizontally disposed electrodes.

4. An electron-discharge device comprising an evacuated envelopecontaining an electron-sensitive screen having a light-emissive area anda secondary-electron emissive signal-generating area, a collectorelectrode disposed adjacent to said signal-generating area in a positionto collect secondary-electrons from said area, an electron gun forgenerating a beam of electrons, said gun being disposed in a position toactivate said light-emissive and signal-generating areas of said screen,horizontal and vertical beam-deflecting elements disposed exterior ofsaid envelope intermediate said gun and screen, and auxiliarybeam-deflecting elements mounted within said envelope for applyingVernier deecting forces to vsaid beam in accordance with signals pickedup by said collector electrode from said secondaryelectron emissivesignal-generating area of said screen.

5. The invention as set forth in claim 4 and wherein said light-emissivearea of said screen comprises a plurality of sub-elemental phosphorareas, and said signal-generating area comprises a plurality ofsecondary-electron emissive signalgenerating indicia individual to saidsub-elemental phosphor areas.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,305,646 Thomas Dec. 22, 1942 2,441,296 Snyder, Jr May 1l,1948 2,446,440 Swedlund Aug. 3, 1948 2,463,535 Hecht Mar. 8, 19492,490,812 Huffman Dec. 13, 1949 2,496,633 Llewellyn Feb. 7, 19502,518,200 Sziklai et al. Aug. 8, 1950 2,621,245 Kell Dec. 9, 19522,630,548 Muller Mar. 3, 1953 FOREIGN PATENTS Number Country Date868,403 France Sept. 29, 1941

